The King's Quest Wiki tells many sad stories concerning the eighth entry in the series, including the reason for the lack of a Roman numeral - Roberta Williams didn't want people to associate this travesty with the earlier, good games in the series. Okay, I paraphrase, but the fact remains that this game isn't very good, and Sierra knew it. It abandons everything that the King's Quest series had - interesting stories, challenging puzzles, and the beloved main characters of the royal family of Daventry. (Not that the women were particularly beloved anymore after King's Quest VII.) Instead, Sierra decided that, since adventure games were on their way out (just ask Lucasarts, right?), they would tap into a genre that was growing in popularity - the first-person shooter.
No, I'm not kidding. Mask of Eternity features a brand new main character, who can run, jump, and fight with melee and projectile weapons, and a first-person perspective that's about the only way to use a crossbow reliably. The engine was developed separately by a company that ultimately failed to produce the actual engine, and they finally rushed it to the street without any QA, making it the first game I ever played that required a downloaded patch to be completed. Not that I blame the testers for not wanting to play the game - it was huge by 1998 standards, requiring so much hard drive space for each area that the game had to uninstall and reinstall itself each time the player moved to a different place. And even now that we have terabyte hard drives, there's no way I know of to get around that. (I'm sure there's some sort of patch out there for it, but that would ruin the experience and cheapen the LP.)